Food Firmicutes and Lactic Acid Bacteria

Vocabulary flashcards covering Firmicutes, cell wall composition, fermentation pathways, lactic acid bacteria genera, hemolysis types, and clinical Streptococcus species from lecture notes.

Firmicutes

A phylum of Gram-positive bacteria named from "firmus" (strong) and "cutis" (skin), characterized by cells with strong walls and comprising more than 270 known genera.

Peptidoglycan

A cell wall polymer composed of alternating $N$-acetylglucosamine (GlcNAc) and $N$-acetylmuramic acid (Mur2Ac) connected by $\beta(1\rightarrow 4)$ linkages, cross-linked by pentaglycine chains and cleaved by lysozyme.

Wall Teichoic Acid (WTA)

Teichoic acids covalently bound to peptidoglycan by a phosphodiester linkage to the C6-hydroxyl of $N$-acetylmuramic acid via a linkage unit.

Lipoteichoic Acid (LTA)

Teichoic acids anchored to the cytoplasmic membrane of Gram-positive bacteria by a glycolipid, specifically diglucosyldiacylglycerol.

Lactic Acid Bacteria (LAB)

A group of Gram-positive, nonspore-forming, catalase-negative, acid-tolerant, and nutritionally fastidious bacteria that rely on fermentative metabolism to generate ATP with lactic acid as the major end product.

Homolactic Fermentation

A fermentation pathway of glucose utilizing glycolysis through the Embden-Meyerhof-Parnas (EMP) pathway and lactate dehydrogenase to yield 2 lactic acid molecules and 2 ATP under anaerobic conditions.

Heterolactic Fermentation

A fermentation pathway of glucose utilizing the phosphoketolase pathway and lactate dehydrogenase to yield 1 $\text{CO}_2$, 1 lactic acid, 1 ethanol, and 1 ATP under anaerobic conditions.

Genus Lactobacillus

A very diverse genus of lactic acid bacteria shaped as rods in chains that can be homofermentative or heterofermentative and grows at both $10^\times\text{C}$ and $45^\times\text{C}$.

Genus Lactococcus

A genus of cocci-shaped lactic acid bacteria that does not produce $\text{CO}_2$ from glucose, grows at $10^\times\text{C}$, belongs to Lancefield Group N, and is used in cheese fermentation.

Genus Streptococcus

A genus of cocci-shaped lactic acid bacteria forming chains that do not produce $\text{CO}_2$ from glucose, grow at $45^\times\text{C}$, and include Lancefield Groups A, B, and pathogenic species.

Genus Pediococcus

A genus of cocci-shaped lactic acid bacteria forming tetrads that do not produce $\text{CO}_2$ from glucose, exhibit high salt tolerance, and grow at both $10^\times\text{C}$ and $45^\times\text{C}$.

Genus Leuconostoc

A genus of cocci-shaped lactic acid bacteria that produces $\text{CO}_2$ from glucose (heterofermentative), grows at $10^\times\text{C}$, and is relevant to vegetable fermentation and food spoilage.

Probiotics

Living microorganisms ingested to improve the intestinal ecosystem of humans and animals, most commonly represented by LAB strains such as Lactobacillus reuteri and Lactobacillus acidophilus.

$\beta$-Hemolysis

The type of hemolysis where bacterial enzymes completely break down both red blood cells and hemoglobin.

$\alpha$-Hemolysis

The type of hemolysis where bacterial enzymes break down red blood cells but not hemoglobin, causing oxidation by $\text{H}_2\text{O}_2$ and green discoloration on blood agar.

$\gamma$-Hemolysis

The absence of any red blood cell hemolysis or breakdown on blood agar.

Serology

The diagnostic examination of blood serum with regard to the response of the immune system to pathogens or introduced foreign substances.

Lancefield Grouping

A classification system based on serological identification of carbohydrate antigens in the cell envelope, dividing streptococci and other LAB into groups A through N.

Streptococcus pyogenes

A Group A, $\beta$-hemolytic, bacitracin-sensitive, PYR test-positive bacterium that causes strep throat, impetigo, scarlet fever, toxic shock syndrome, and necrotizing fasciitis.

Streptococcus agalactiae

A Group B, $\beta$-hemolytic, bacitracin-resistant, CAMP test-positive bacterium causing genital tract infections in pregnant women, newborn sepsis/meningitis, and animal mastitis.

Enterococcus faecalis

A Group D lactic acid bacterium that can show $\text{\textbackslash{}alpha}$, $\text{\textbackslash{}beta}$, or $\text{\textbackslash{}gamma}$ hemolysis, grows in $6.5\text{y}\text{NaCl}$, and tests positive on the PYR test.

Streptococcus pneumoniae

An $\text{\textbackslash{}alpha}$-hemolytic, non-groupable bacterium that is bile soluble and inhibited by optochin, causing pneumonia, bacteremia, meningitis, arthritis, and sinusitis.

Viridans Group Streptococci

A group of non-groupable, $\text{\textbackslash{}alpha}$-hemolytic oral streptococci (such as Streptococcus mutans) that are not bile soluble and are not inhibited by optochin.

Streptococcal Pharyngitis

An infection caused by Group A $\text{\textbackslash{}beta}$-hemolytic streptococci (Streptococcus pyogenes) characterized by a sore throat and typical tonsillar exudate.